{1}\{1\}{1}
R−{32} \mathrm R- \{\frac{3}{2}\}R−{23}
R−{1,−1} \mathrm R - \{1, - 1\}R−{1,−1}
{x∈R:x≠1} \mathrm {\{x ∈ R : x \ne 1\}}{x∈R:x=1}